K. Yamaguchi et al., POLYMERASE CHAIN REACTION-BASED APPROACHES FOR DETECTION OF ALLELIC LOSS IN THE P53 TUMOR-SUPPRESSOR GENE IN COLON NEOPLASMS, The American journal of gastroenterology, 92(2), 1997, pp. 307-312
Objectives: Inactivation of the p53 tumor suppressor gene is considere
d to be a late event involved in the malignant transformation of color
ectal adenoma to cancer. Thus, its detection is thought to provide use
ful information for the clinical management of colorectal neoplasms. W
e devised a rapid screening test for allelic loss of the p53 gene by n
on-radioisotopic single-strand conformation polymorphism analysis. Met
hods: Biopsy materials from 119 colorectal tumors obtained at endoscop
y were examined. Three intragenic polymorphic sites were amplified by
polymerase chain reaction using DNA extracted from these materials, an
d amplified DNA fragments were subjected to non-radioisotopic single-s
trand conformation polymorphism. Results: This method can detect a los
s of heterozygosity (LOH) of the p53 locus from samples containing ove
r 40% tumor derived DNA, and the combination of the three polymorphic
markers encompassed 62.4% of Japanese patients as informative. In aden
ocarcinoma, an LOH was detected in 51.5% (17 of 33) of the samples and
in 12.2% (4 of 33) of tubular and/or tubulovillous adenomas. The p53
gene was mutated only in samples carrying an LOH, that is 64.7% (11 of
17) of carcinomas and 25.0% (1 of 4) of adenomas, but there were no m
utation in samples retaining both alleles. The presence of an LOH was
statistically correlated both with p53 mutation and malignant histolog
y (chi(2) test, p < 0.05). Conclusions: This method can detect LOH fro
m biopsy material obtained at endoscopy. LOH in the p53 locus precedes
mutation of the p53 gene, and its detection provides useful informati
on of malignancy in colorectal tumors.